One Universe at a Time

Modified Gravity Need Not Apply

In the battle to describe the motion of galaxies, two models fight head to head. In one corner is dark matter, a strange form of matter that surrounds galaxies, and can be seen only through its gravitational tug on light. In the other corner is Modified Newtonian Dynamics (MoND), which proposes a new approach to gravitational interactions, just as Einstein’s model superseded Newton’s.

The team developed a computer model that accounted not just for stars and dark matter, but also the interstellar gas. In modeling the formation and evolution of galaxies, they found that a correlation forms between the distribution of matter and their rotation. They also found the relation between mass, size and luminosity of galaxies in their model matched that of observed galaxies.

So dark matter can account for the rotational dynamics of a galaxy just as MoND models can. That doesn’t rule out MoND, but it does mean that MoND isn’t necessary in this case.